1. Technical Field
The disclosure generally relates to abrasive compacts that are more easily formed for example, into useful geometries.
2. Description of the Related Art
Abrasive compacts are used in drilling, boring, cutting, milling, grinding and other material removal operations. Abrasive compacts consist of ultra-hard particles sintered, bonded, or otherwise consolidated into a solid body. Ultra-hard particles may be diamond, cubic boron nitride, carbon-nitride (CN) compounds, boron-carbon-nitrogen-oxygen (BCNO) compounds or any material with hardness greater than boron carbide. The ultra-hard particles may be for example single crystals or a polycrystalline aggregates.
In commerce, abrasive compacts may be known as diamond or polycrystalline diamond (PCD) compacts when based on diamond, or polycrystalline cubic boron nitride (PCBN) compacts when based on cubic boron nitride (cBN). Abrasive compacts from which residual sintering catalysts have been removed may be called leached or thermally stable compacts. Abrasive compacts integrated with cemented carbide substrates are referred to as supported compacts. Supported abrasive compacts include a cemented carbide substrate to increase impact resistance, strength, as well as simplify the attachment of abrasive compacts to engineering structures.
Abrasive compacts are manufactured in large disks referred to as “blanks” or “tool blanks” from which individual cutting tips are cut using many different methods.
Abrasive compacts essentially based on a single ultra-hard phase, for example diamond or cubic boron nitride are well known. These abrasive compacts however are extremely hard and therefore difficult to grind or otherwise fabricate into useful components of controlled dimension with smooth or defect-free surfaces. The expense of abrasive machining, laser cutting, or plasma machining is substantial and limits the commercial application of abrasive compacts. One solution has been to produce abrasive compacts with ultra-hard particles and less hard phases. However, these compacts have not provided better commercial properties, and are typically defective as the presence of the less hard phases disrupts the function of the sinter catalyst.
Defects in abrasive compacts refer to cracks, chips, pits, delaminations internal or surface, spots and abrasive layer or overall tool blank shape distortion, of varying scale and degree. Defects are undesirable as they will impair tool strength and tool life or yield of useful tools from a blank.
U.S. Pat. No. 4,016,736 describes a diamond and cubic boron nitride compact wherein the thermal resistance of cubic boron nitride is exploited. U.S. Pat. No. 4,797,241 describes an abrasive compact comprising a mixture of PCD and PCBN, each independently sintered. U.S. Pat. No. 6,759,128 describes a sintered mixture of B—C—N new solid phase. U.S. Pat. Nos. 6,772,849, 4,734,339, 5,755,299 all describe boride-coated PCD for drill bits. U.S. Pat. No. 5,697,994 describes compacts comprising diamond and cubic boron nitride for enhanced corrosion resistance. However, none of these references describe hardness control or improved fabrication of compacts.
U.S. Patent Publication No. 2003/0019106 and U.S. Pat. No. 6,596,225 describe the use of hexagonal boron nitride as an unreactive mold coating. The boron nitride is not part of the abrasive compact.
High-pressure sintering of abrasive compacts with a catalytic liquid phase, typically molten Fe, Ni, Al, Co, Mn, W, alloys or blends thereof is also well known. Typically, catalyst is provided by blending metal particles with the ultra-hard particles or by contact with an external metal-containing source. The catalyst metal is melted and infiltrated into the compacted ultra-hard abrasive powders. Conformal contact of molten metal at ultra-hard particle contact points allows intergranular bonding to occur. When the molten metal contact is of sufficient duration and spatially uniform, the ultra-hard particles are dissolved and may be reprecipitated or recrystallized to provide a continuous matrix of high quality bonds between ultra-hard particles. The high quality bonds formed during compact sintering produce a compact with high hardness, approaching the value of the single-crystal ultra-hard phase. In addition to high hardness, the strong bonds formed between ultra-hard particles combined with a low level of microstructural defects impart high strength, high abrasion resistance, high heat tolerance and useful fracture toughness to the compact. This combination of properties has, heretofore, also dictated that the compact is extremely difficult to grind or otherwise form into useful shapes. Abrasive machining, laser cutting, and high energy plasma machining has been required as subsequent processing steps to produce a commercially useful tool blank.
It is also known that incomplete and/or non-uniform contact with, or unstable reactions of, the catalytic molten metal with the ultrahard grits produces a compact with lower quality interparticle bonds and increased defects. This defective compact may be less difficult to machine, but it will not provide the abrasive performance required for utility. It may simply crack or delaminate upon use. Thus an abrasive compact with coincident controlled hardness, useful toughness, strength and improved ease of fabrication is not known.
Accordingly, there is a need for a product or compact in which machinability is independently increased while maintaining high levels of hardness, strength and toughness by a process that is cost efficient.
The disclosure contained herein describes attempts to address one or more of the problems described above.